From the cognitive health one:
This study has several limitations. The predominantly male, overweight-to-obese sample may limit generalizability to broader populations, including women and individuals with lower baseline adiposity. Although initial fat loss occurred under randomized conditions within the original trials, the 5–16-year follow-up did not involve random assignment to post-trial behavior patterns, limiting causal inference. Dietary and lifestyle patterns at follow-up were systematically assessed, and the MED diet adherence score was included in all multivariable models to account for post-trial behaviors. This adjustment also addresses the possibility that participants who responded well to the intervention were inherently more likely to maintain healthy dietary patterns over time, which may have independently supported brain health. … Additionally, while follow-up MRI scans were analyzed for participants across all four trials, baseline and end-of-intervention abdominal adipose tissue scans were available only from CENTRAL and DIRECT-PLUS trials, and brain MRI scans were available only from the DIRECT-PLUS trial. Consequently, long-term associations between adipose depots and brain outcomes were **limited to a 5- and 10-year follow-up for adipose depots and a 5-year follow-up for brain MRI. Importantly, cognitive function was not systematically measured at pre- or post-intervention time points, limiting the ability to assess individual-level cognitive changes over time. **A further limitation is the absence of quantitative MRI measures of ectopic fat in organs such as the liver and pancreas, which are recognized as relevant to cardiometabolic and brain health. … [Emphasis mine]
The MED score mentioned is 14 questions including how many tablespoons of oil you consume in a week. Self reported data about diet covering a month would barely be reliable let alone the 5 or ten years, but it’s brushed off as being good enough to lean towards causation rather than correlation.
You (and the paper) are way too comfortable with claiming causation. The MED score was used specifically to reduce the possibility that there was another cause for both the lowered visceral fat and the cognitive measures and assumes the original interventions caused VAT reduction. If there is a known dietary intervention that works over 5 or 10 years to reduce weight, that alone would be a miracle since I’ve never seen any study of an intervention that can even guarantee a ten percent loss sustained over two years excepting gastric bypass. Self reported data about ones diet over five or ten years is practically worthless in my eyes. Can you tell me how many ounces of food your lunch was exactly one month ago? Neither could the participants. I bet their levels of physical activity may fluctuate year by year as well, especially at the age many of the participants were at. How many MET hours is also something typical people will not be able to accurately know or give a meaningful answer that covers 5 or 10 years.
Bad data does not lead to a strong conclusion.